Laccotrephes tristis is a species of water scorpion also commonly known as a toe-biter, that occurs Australia-wide and is part of the family Nepidae.

[2][4] Laccotrephes tristis is brownish in colour with a broad oval shaped, flat body, at a length of 11-45mm.

[2] They have often been seen covering their back with mud concealing themselves from view and waiting with their heads pointed in the direction of deeper water.

[2] This particular species is also a strong flier, with well developed wings, however flight is very rarely observed.

[2] Water scorpions are a carnivorous ambush predator, hunting on the edges of shallow creeks or pools.

[2] Once the prey has been caught the water scorpion inserts its rostrum into the body of the victim and injects enzymes that liquify the insides.

Water scorpions feed on a variety of aquatic animals, such as tadpoles, small fish, and mosquito larvae.